Retrotransposons are important retroviral agents capable of integrating within actively transcribing genes, and attributes to the appearance of numerous cancers and tumors among humans and animals. Our long-range goal is to understand the mechanisms involved during target site selection and insertion of the LTR-retrotransposon, Tfl, in Schizosaccharomyces pornbe. The objective of this application, which is the next step toward attainment of our long-range goal, is to analyze target site sequence requirements, and 3' processing mechanisms of viral cDNA that are involved during integration. The central hypothesis for the proposed application is that alterations within Tf1 target site sequences will change the preferred region of specificity during insertion, and that Tf1 shares a similar method of 3' processing observed in the retrovirus HIV-1. The rationale for the proposed research is that these regions of specificity will make possible the identification of host and viral proteins involved during insertion, and therefore, the design of antiviral agents that will prevent or control integration. The central hypothesis will be tested and the overall Objective of this application accomplished by pursuing the following two specific aims 1) Identify mechanistic basis for target site selection, and 2) Isolate and characterize viral intermediates during Tf1 integration. The proposed research project is innovative, because Schizosaccharomyces pombe has several biological similarities to higher-order eukaryotes, and presents a well-developed system by which retroviral elements can be genetically studied. It is our expectation that findings from this study will reveal why certain sequences of the genome are preferred for insertion of retroviral agents and the parallel function of the integrase protein with that of the retroviruses. This study is expected to enhance knowledge concerning retroviral target site selection. The proposed research is significant, because the studies will generate new information concerning target site selection of the retroviral agent, If 1, in a mammalian-like host. The proposed research project will be of additional significance because support from the AREA program will: 1) allow Delaware State University (DSU), a minority serving institution, to benefit from a research environment strengthened through an AREA award, 2) expose DSU students to biomedical research that will encourage them to pursue graduate studies in the health sciences, and 3) allow the principal investigator supported under the AREA award to benefit from the opportunity to conduct state-of-the-art independent meritorious research.